The present invention relates to a drive controller for a cargo handling vehicle including an engine, a generator motor, and a travel motor, which are arranged coaxially with one another.
Japanese Laid-Open Patent Publication No. 2005-298163 describes a prior art example of a drive controller for a cargo handling vehicle. The cargo handling vehicle includes an engine, a generator-motor, and a cargo handling pump, which are arranged so as to be coaxial to one another. The cargo handling vehicle also includes a travel motor, which is used when the vehicle travels, and a battery, which supplies power to the generator motor and travel motor. The cargo handling vehicle switches the operation modes of the generator-motor between generator mode and motor mode. More specifically, when a cargo handling operation does not require a high output, the generator-motor is switched to the generator mode, and the pump is driven by the engine. When a cargo handling operation requires a high output, the generator-motor is switched to the motor mode.
When such a cargo handling vehicle of the prior art travels, the generator motor often generates power to drive the travel motor. When the cargo handling vehicle climbs up a slope while carrying cargo at the maximum load, the power used to drive the travel motor increases. This increases the power required to be generated by the generator motor. When such cargo handling is performed as the cargo handling vehicle travels, the cargo handling load and power generation load applied to the engine may lower the cargo handling speed. Thus, when the cargo handling vehicle travels while handling cargo, the generator motor and travel motor must be controlled so that such a problem does not occur.